This invention relates to a novel method for printing intelligible information, particularly, although not exclusively, to printing an identification marking on the surface of a rigid body.
Many electron tubes are made by providing a vacuum-tight envelope and then sealing an electron-gun mount assembly into the envelope. Most factories have not one but many different electron-gun mount assemblies in stock and in process, which assemblies are used on the different tubes that are assembled. These assemblies are very similar in appearance and require identification marks on them to prevent mixups.
It has been proposed previously to print the identifications marks directly on the support rods of the mount assembly by a transfer process. The rods are rigid bodies, usually of glass, with somewhat irregular surfaces. The marks are to be printed at the same time as an arc-suppressing conductive patch is printed. In the prior transfer process, shallow depressions the shape of the desired marks in a plate are filled with viscous printing medium as by doctor blading. Then, a resilient ball having a nonabsorbent surface is impressed over the depressions, transferring printing medium in the desired shape to the surface of the ball. Then, the ball is impressed onto the receiving surface thereby transferring medium in the shape of the desired marks.
This prior method has disadvantages as well as advantages. A different plate is required for each different marking, requiring a large inventory of plates as well as separate setups for each different plate. The depressions in the plates are etched chemically or electrically, and after relapping, as is required from time to time, must be re-etched to the required depth. Thus, the plates, their maintenance, and their use are more expensive than is desirable.